In recent years, a liquid crystal display device is used to display visible information in a wide variety of applications such as a navigation system, television, palm-top computer, electronic personal organizer, portable telephone, etc. In the production of liquid crystal display devices, one known technique to mount a semiconductor device such as a driver integrated circuit on a liquid crystal panel is to directly mount the semiconductor device on one of a pair substrates facing each other via a liquid crystal. This technique is called the COG (chip on glass) technique. It is expected that the COG technique will contribute to further reductions in the size and weight of liquid crystal display devices and also to an improvement in the connection pitch.
In conventional COG type liquid crystal display devices, a plurality of input connection terminals are formed on a substrate, and input bump electrodes of a liquid crystal driver IC are directly connected to the input connection terminals using a connection element such as an ACF (anisotropic conductive film). Furthermore, output connection terminals of an apparatus using a liquid crystal display, such as a portable telephone, are formed on an FPC (flexible printed circuit), and the FPC is connected to the input connection terminals. The connection between the FPC and the input connection terminals is generally made using an ACF.
In the conventional COG type liquid crystal display device, since the FPC is connected to the input connection terminals using the ACF, a thermo-compression bonding process is necessary to make the connection. However, the thermo-compression bonding process can cause a residual stress, which in turn causes the liquid crystal panel or the liquid crystal driver IC to receive a force arising from the residual stress. Heat generated during the thermo-compression bonding process can cause the ACF connecting the liquid crystal drive IC to the substrate to become soft, which in turn causes a trouble associated with the contact between the liquid crystal driver IC and the substrate. Although the problem associated with the connection of the liquid crystal driver IC may be avoided by performing the thermo-compression bonding process at a temperature lower than the softening temperature of the ACF connecting the liquid crystal driver IC to the liquid crystal panel, the reduction in the thermo-compression temperature can cause another problem associated with the reduction in the bonding strength.